An example of a conventional decimal multiplying device is shown in FIG. 1, in which each of a decimal N-digit multiplicand and a decimal M-digit multiplier is converted to a binary-coded decimal operands by a decimal-to-binary converter 11 or 12 before multiplication thereof. Multiplication is carried out by a software program for calculating a product of binary-coded decimal operands in a binary mutiplying member 13, the output of which is then converted again to a final decimal product by a binary-to-decimal converter 14.
With another conventional decimal multiplying device, a decimal multiplication table for decimal operands of limited digits in length is stored in a memory of the multiplying device. The table is retrieved as many times as necessary according to the numbers of digits of the multiplier and the multiplicand to be calculated. The resultant data of each retrieval is collected and combined together for obtaining the decimal product by a software program.
Each of the conventional multiplying devices as described above has a disadvantage in which the software program for calculating a product is complicated, hence requiring a large amount of time when the size of the multiplier and the multiplicand are large in length.